This invention relates generally to engines, and more particularly to fuel injectors with the ability to inject fuel at two different pressures during a single injection event.
High pressure common rail fuel injection systems and electronic unit pump fuel injection systems are becoming more widespread for use with diesel engines. Engineers have learned that improved control over the injection event of fuel injectors used in these and other fuel injection systems can reduce emissions produced during injection. One attempt at controlling the injection event is disclosed in U.S. Pat. No. 3,627,208, issued to Scott et al. on Dec. 14, 1971. Scott et al. teaches a fuel injector including a mechanically controlled pressure reducing valve that purports to control injection pressure during the injection event. The pressure reducing valve taught in Scott et al. purports to allow delivery of fuel to the nozzle outlet at either a relatively low pressure or a relatively high pressure. While the pressure reducing valve taught in Scott et al. has increased control over an injection event, there is room for improvement. For instance, it is believed that an even greater degree of control over the injection event can further improve emissions that are produced during an injection event.
The present invention is directed to overcoming one or more of the problems as set forth above.
In a first aspect of the present invention, an engine includes an engine housing. A plurality of fuel injectors are positioned within the engine housing, each of which has an injector body that defines a fuel inlet and a nozzle outlet. Attached to the injector body is an electronic actuator. An injection pressure control valve member is positioned in the injector body and is operably coupled to the electronic actuator. The injection pressure control valve member is movable between a first position in which the fuel inlet is fluidly connected to the nozzle outlet via a relatively restricted flow path, and a second position in which the fuel inlet is fluidly connected to the nozzle outlet via a relatively unrestricted flow path. A needle valve member is positioned in the injector body and is movable between a closed position blocking the nozzle outlet and an open position.
In another aspect of the present invention, a fuel injector includes an injector body that defines a fuel inlet that is separated from a nozzle outlet by at least two passageways. An electronically controlled valve is attached to the injector body and is movable between a first position in which one of the at least two passageways is closed and a second position in which said one is open. A needle valve member is positioned in the injector body and is movable between a closed position blocking the nozzle outlet and an open position.
In yet another aspect of the present invention, a method of controlling fuel injection includes providing an engine that includes a fuel injection system having a plurality of fuel injectors that each include an injector body that defines a fuel inlet and a nozzle outlet and is operably connected to an electrical actuator. The fuel inlet and the nozzle outlet of a first fuel injector are connected via a relatively restricted fuel passageway, in part by activating the electronic actuator. A first amount of fuel is the n injected from the first fuel injector. Next, t he fuel inlet and the nozzle outlet of the first fuel injector are connected via a relatively unrestricted fuel passageway, in part by deactivating the electronic actuator. A second amount of fuel is then injected from the first fuel injector.